Directory service for a computer network

ABSTRACT

A distributed directory service for an on-line services network comprises multiple, separate services, referred to as “Directory Service Providers,” running on respective groups of application servers. Each Directory Service Provider stores and provides access to a respective hierarchical directory structure, with nodes of the directory structures representing the various on-line services and other content entities which may be accessed by end users of the network. Junction point nodes are used to provide user-transparent links between the different directory structures, so that the directory structures appear to end users as a single, hierarchical directory. A common application program interface (API) is implemented by all Directory Service Providers, allowing client applications running on computers of end users to access the different directory structures using a common set of software methods. Data items that are shared by multiple nodes, such as icon bitmaps and sound files, are optionally stored by the Directory Service Providers within a shared database (separately from the nodes), and are accessed via special API methods. Various forms of node filtering, including language-based filtering and access rights filtering, are performed by the Directory Service Providers to determine which nodes to show to end users.

RELATED APPLICATION

This application is a continuation-in-part of copending U.S. applicationSer. No. 08/485,493, filed Jun. 7, 1995, having the title TRANSACTIONREPLICATION SYSTEM AND METHOD FOR SUPPORTING REPLICATEDTRANSACTION-BASED SERVICES.

FIELD OF THE INVENTION

The present invention relates to computer networks, and moreparticularly, relates to a system and method for providing users with adirectory of the content of a computer network.

BACKGROUND

On-line services networks commonly provide end users with access to avariety of different types of content entities. These content entitiesmay include, for example, executable programs that can be downloaded tothe user's computer, communications services (such as chat and emailservices) that allow users to communicate with one another, bulletinboard system (BBS) services that allow users to review postings onvarious topics, and publications services that provide users with accessto old and new printed publications. The various content entities aretypically made available to users via a network directory system whichpresents users with a hierarchical view of the network's content.

In copending U.S. application Ser. No. 08/472,807 having the titleARCHITECTURE FOR SCALABLE ON-LINE SERVICES NETWORK, filed Jun. 7, 1995,there is described an on-line services network architecture in which thevarious user-accessible content entities are distributed on a number ofdifferent servers of a network. For example, one group of servers runs aBBS service application (and stores all BBS postings), while anothergroup of servers runs a Chat service. Various benefits are realized bythis architecture over conventional, mainframe designs. For example, thenetwork can easily be scaled in size to accommodate increased numbers ofusers.

The present invention is directed generally to the problem of providingan extensible directory service for a distributed on-line servicesnetwork, such as a network of the type described in the above-referencedapplication. One goal of the invention is to provide users with ahierarchical view of a distributed network's content such that thedistribution of content entities among different servers is not apparentto the end user. Another goal is to provide a directory that is seen byusers as a single, homogeneous directory, rather than a collection ofseparate directories. Another goal is to provide a directory servicethat operates efficiently over a low-bandwidth communications channel,so that users do not experience significant delays while accessing thedirectory service over a wide area network. Another goal is to provideeach user with a directory that is tailored to that user's particularaccess rights on the network. Another goal is to provide a directoryservice that is highly extensible, so that new content entities andentity types can easily be added as the network evolves. Another goal isto provide a directory service that is highly scalable in both contentcapacity and user capacity.

SUMMARY

In accordance with the present invention, a distributed directoryservice for an on-line services network is provided. The directoryservice comprises multiple different services, referred to as “DirectoryService Providers,” running on respective groups of application servers.Each Directory Service Provider stores and provides user access to arespective hierarchical directory structure (preferably in the form of adirected acyclic graph) which represents a subset of the content (i.e.,the on-line services and service-related entities) available to users ofthe network. In a presently preferred implementation, the directoryservice includes two Directory Service Providers: a BBS service whichprovides a directory to BBS content, and a “Dirsrv” service whichprovides access to all other types of content. Users that connect to theon-line services network via a wide area network (WAN) can access thedirectory service to interactively explore and access the content of thenetwork.

Each hierarchical directory structure preferably includes a plurality ofinterconnected nodes, including leaf nodes, folder nodes and junctionpoint nodes. The leaf nodes represent specific services or serviceentities (such as Chat rooms, BBS messages, and download-and-run files)which may be accessed by users. The folder nodes represent collectionsof related leaf nodes, and are generally analogous to directories withina file system. The junction point nodes act as proxies for nodes(referred as “target nodes”) of other directory structures, and providea mechanism for allowing users to move from one Directory ServiceProvider to another while exploring the content of the network. Thejunction point nodes thereby integrate the various directory structuresinto a single, hierarchical “content tree” from the viewpoint of endusers.

Each node of the content tree, whether a leaf node, folder node orjunction point node, includes a variable-length list of properties.These properties may include, for example, various character stringproperties which may be viewed by end users (such as a descriptionproperty which provides a written description of the correspondingcontent), and various non-viewable properties which contain, forexample, information needed to launch the appropriate client and servercomponents of a corresponding-on-line service.

A preferred client application of the directory service reconstructs thehierarchical content tree on the screens of users, with the variousnodes shown as corresponding icons (which are downloaded from thedirectory service) and/or textual names. Using the client application,users can navigate the content of the network by, for example, expandingfolder nodes to expose lower levels of nodes, and by requesting theparents of a node to move upward within the content tree. Users can alsoview properties of nodes, and can open various on-line services (by, forexample, double-clicking the icon of a leaf node).

In accordance with one aspect of the present invention, the specificactions that can be performed by a user at a given node depend upon theparticular access rights of the user at the node. For example, a userwith “view-only” level access rights at a node may only be permitted toview a limited set of properties (such as the description) of the node,while a user with “user” level privileges may be able to view theproperties of the node and open a service that corresponds to the node.Users with “sysop” level privileges are advantageously given thecapability to remotely edit certain properties of nodes. (As describedbelow, a user may have no access rights at a node, in which case theuser will not be able to see even the icon or the name of the node.) Theaccess rights of users may vary from user-to-user and from node-to-node.In the preferred embodiment, the access rights of users are storedwithin an access rights database, and are obtained by the directoryservice using an API method which generates user-specific queries of theaccess rights database.

In accordance with another aspect of the invention, each node has a setof “local properties” that are stored locally by the respectiveDirectory Service Providers, and may also have one or more “remoteproperties” that are provided by the remote service to which the nodecorresponds. Remote properties are advantageously stored by theDirectory Service Providers within node-specific remote property caches.When a remote property of a node is requested by a client application,the Directory Service Provider initially checks the node's remoteproperties cache, and if the property is not found, forwards the requestto the “remote” service to which the node corresponds. For example, arequest for a remote property of a Chat room node would be forwarded bythe Directory Service Provider to the Chat service. When the remoteproperty is returned by the service, the Directory Service Providerreturns the property to the client, and caches the property within thenode's remote properties cache. The remote properties caches arerefreshed periodically to ensure that the remote properties storedtherein are up-to-date.

The remote properties feature of the present invention advantageouslyallows service data that changes frequently (such as the number ofoccupants of a Chat room) to be provided dynamically by the end servicesto which the nodes correspond. The remote properties feature is alsouseful for allowing certain properties of junction point nodes to bestored remotely by the Directory Service Provider of the junctionpoint's target node.

In accordance with another aspect of the invention, a navigationapplication program interface (API) is provided which allows clientapplications to request node properties and other information needed toprovide users with a navigable, hierarchical view of the content tree.This API is advantageously implemented (at least in-part) by allDirectory Service Providers, so that a common set of navigation methodscan be used to navigate the entire content tree. The provision of thenavigation API facilitates the addition of new Directory ServiceProviders to the directory service, and thereby provides for a highdegree of extensibility.

In accordance with another aspect of the invention, the methods of thenavigation API allow client applications to specify the particularproperties to be returned, so that only those properties needed by theclient applications are transmitted over the WAN. This advantageouslyconserves WAN bandwidth, and increases performance from the viewpoint ofthe user.

In accordance with another aspect of the invention, each time a clientapplication requests the properties of a node (by for example, calling aGetChildren method of the navigation API to obtain all children of acurrent node), the directory service checks the user's access rights tothe node. If the user has no access rights with respect to the node(i.e., is not authorized to access the node), the directory service doesnot return the requested properties, and thereby prevents the user fromseeing the node. Each user is thus provided with a user-specific,access-rights-filtered directory, seeing only those nodes (e.g., icons)to which the user has at least some access rights. This feature allowscertain content objects (such as private folders of subgroups of users)to be completely hidden from certain classes of users, and therebyprovides for a high degree of security against the unauthorized accessto such objects.

In accordance with another aspect of the invention, a method is providedfor allowing users to specify language and geographic region filters,and for using these filters to limit the nodes that are returned to theclient application. In a preferred embodiment, the user-specifiedfilters are passed to the directory service via a “locales” parameter ofa navigation API method, and are compared against a locales list whichis (optionally) stored as a property of each node. Nodes which do nothave the locales (i.e., languages and/or. geographic regions) specifiedby the user are not returned. The user is thus provided with acustomized, filtered directory of the network's content. This featurealso conserves bandwidth over the WAN by preventing downloads of nodesin which the user has no interest.

In accordance with yet another aspect of the invention, the DirectoryService Providers optionally store certain types of shared data items(i.e., data items that are shared by multiple nodes) within a shareddatabase, rather than as properties of the nodes. Duplicate copies ofshared data items on the same application server are thereby avoided. Inthe presently preferred implementation, icon bitmaps, sound files,banner objects and download-and-run files are stored within the shareddatabase, and the nodes of the content tree have correspondingproperties (Icon ID, Soundfile ID, Banner ID and Drfile ID) which can beused to reference these shared data items. Thus, for example 10different nodes may share the same icon, in which case each such nodewill have the ID of the shared icon stored as an Icon ID property.Special methods of the navigation API provide for the downloading of theshared data items and for the enumeration of the shared data items of agiven type.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now be described withreference to the drawings of a preferred embodiment, which is intendedto illustrate and not to limit the invention, and in which:

FIG. 1 is a high-level diagram illustrating the general architecture ofan on-line services network which embodies the present invention.

FIG. 2 illustrates how the content of the on-line services network ofFIG. 1 is preferably mapped into multiple hierarchical, tree-likedirectory structures of nodes, with each node being in the general formof a list properties.

FIG. 3 illustrates a preferred graphical user interface which presentsusers with a hierarchical, navigable view of the content of thedirectory structures of FIG. 2.

FIG. 4 illustrates the primary client and server components that may beinvoked as a user browses the content of the network, via a preferredembodiment of a directory service.

FIG. 5 illustrates a node table which represents the basic propertiesinformation associated with each node of the directory structures ofFIG. 2.

FIG. 6 illustrates a preferred format for a node file.

FIG. 7 illustrates a preferred process by which client applicationsrequest, download and cache icon bitmaps that are stored by thedirectory service of FIG. 4.

FIG. 8 illustrates the primary memory structures implemented on eachapplication server of the Dirsrv service group of FIG. 1, andillustrates the basic calls generated and received by the applicationserver.

FIG. 9 illustrates a preferred process by which a directory serviceapplication server (such as the Dirsrv server of FIG. 8) retrieves andreturns a specific- property requested by a client.

FIGS. 10A and 10B illustrate a preferred method for providing a seamlessinterface between directory namespaces through the use of junctionpoints.

FIG. 11 illustrates a sequence of steps performed on a directory serviceapplication server to determine whether to show a node to a user.

Reference numbers in the drawings have three or more digits; the twoleast significant digits are reference numbers within the drawing, andthe more significant digits indicate the figure in which the item firstappears. For example, reference number 604 refers to an item which isfirst shown in FIG. 6. Like reference numbers indicate like orfunctionally similar components.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Described herein is an extensible directory service which includesmultiple, distinct services running on separate groups of applicationservers. Although the directory service is described with reference to apreferred embodiment of a distributed on-line services network, it willbe apparent to those skilled in the art that various aspects of thedirectory service are applicable to other types of computer networks andnetwork configurations.

For convenience, the description of the preferred embodiment is arrangedwithin the following eleven sections:

1. ARCHITECTURAL OVERVIEW (FIG. 1);

2. OVERVIEW OF DIRECTORY SERVICE AND RELATED COMPONENTS (FIGS. 1-3);

3. CLIENT-SERVER ARCHITECTURE OF DIRECTORY SERVICE (FIG. 4)

4. REPRESENTATION OF NODE PROPERTIES (FIG. 5);

5. NODE DISK STRUCTURES (FIG. 6);

6. SHABBIES (FIG. 7);

7. SERVER MEMORY STRUCTURES AND OPERATION (FIGS. 8 AND 9);

8. JUNCTION POINTS (FIGS. 10A AND 10B);

9. TREENAV METHODS;

10. LOCALES AND ACCESS RIGHTS FILTERING OF NODES (FIG. 11); and

11. OTHER EMBODIMENTS.

The first of these sections provides an architectural overview of thepreferred on-line services network in which the present invention isembodied. The architecture of this network is further described in theabove-referenced application having the title “ARCHITECTURE FOR SCALABLEON-LINE SERVICES NETWORK” (U.S. application Ser. No. 08/472,807), whichis incorporated herein in by reference.

Throughout the following description, the first letters of the names ofspecific services on the network will be capitalized (for example,“Chat,” “BBS,” and “Directory Service”). Additionally, the names ofspecific software methods and interfaces will be provided in mixed case(for example, “GetChildren,” “GetAccountRights” and “TreeNav.”)

1. Architectural Overview (FIG. 1)

FIG. 1 is a high-level diagram illustrating the general architecture ofan on-line services network 100 which provides a directory service inaccordance with the present invention. Multiple client microcomputers102 are connected to a host data center 104 by a wide area network (WAN)106. The wide area network 106 includes WAN lines 108 which are providedby one or more telecommunications providers, and which allow end users(i.e., users of the microcomputers 102) over a wide geographic area toaccess the host data center 104. The WAN lines 108 preferably includeboth X.25 lines and ISDN (Integrated Service Digital Network) lines. Thehost data center 104 provides a variety of information-related andcommunications-related on-line services to end users.

The host data center 104 comprises a plurality of application servers120 connected to one or more high speed local area networks (LAN) 122.The application servers 120 are preferably Pentium-class (or better)microcomputers which are scalable to at least four central processingunits (CPUs), and which run the Microsoft Windows NT operating systemavailable from Microsoft Corporation. Each application server 120typically has at least 128 MB of random-access memory (RAM) and at least4 GB of disk space.

The application servers 120 are arranged into service groups (alsoreferred to as “AppGroups”) that correspond to specific on-lineservices. Three example service groups are shown in FIG. 1: a Chatservice group 130, a Bulletin Board System (BBS) service group 134, anda Dirsrv service group 132. Additional service groups (not shown) areprovided to implement other on-line services, including a Mediaviewservice which provides multimedia titles to end users, a mail service, aComponent Manager service which allows users to update client softwarewhen new releases become available, and a File Transfer Manager (FTM)service. Other on-line services may include, for example, an interactivegames service, a weather service, and a World Wide Web browsing service.A service group can have as few as one application server 120. Systemadministrators can adjust the number of application servers 120 in agiven service group to accommodate the current usage level of thecorresponding service. For example, application servers 120 can be addedto the BBS service group 134 to increase the user capacity of the BBSservice.

Also connected to the LAN 122 are multiple Gateway microcomputers 140(hereinafter “Gateways”) which link incoming calls from end users to theapplication servers 120. The Gateways 140 are preferably Pentium-classmicrocomputers which are scalable to at least four CPUs, and which runthe Microsoft Windows NT operating system. Each Gateway 140 typicallyhas at least 64 MB of RAM and at least 2 GB of disk space, and iscapable of supporting approximately 1000 simultaneous user connections.

Also connected to the LAN 122 are multiple security servers 150. Thesecurity servers 150 are preferably Pentium-class microcomputers whichare scalable to at least four CPUs, and which run the Microsoft WindowsNT operating system. Each security server 150 maintains a relationaldatabase 152 which contains the access rights data for all users of thenetwork 100. Each security server 150 runs Structured Query Language(SQL) code to provide access to its respective access rights database152. SQL is a language standardized by the International StandardsOrganization (ISO) for defining, updating and querying relationaldatabases. A query to the access rights database 152 can emanate eitherfrom one of the application servers 120 (when, for example, a userattempts to access a content entity which is stored by the applicationserver 120), or by one of the Gateways 140 (when a user attempts to openan on-line service). Each machine 120, 140 which generates queries ofthe access rights databases 152 preferably implements an access rightscache for locally storing user-specific access rights informationobtained from the database 152.

Various other types of servers and other microcomputers are connected tothe LAN 122 but are not shown in FIG. 1. For example, billing and logonservers are provided to record billable events and to handle user logon,respectively. Further, Arbiter microcomputers are provided to performtransaction replication services for certain service groups (includingboth the Dirsrv service group 132 and the BBS service group 134),allowing the application servers 120 of such service groups to storeidentical copies of the same service content data.

It is envisioned that the host data center 104 may have on the order ofone hundred Gateways 140, and between several hundred and severalthousand application servers 120. A host data center of this type willbe able to handle millions of subscribers and tens of thousands ofsimultaneous user logon sessions. Advantageously, the processingcapacity of the host data center 104 can easily be increased (to supportnew services, and to support increases in the number of subscribers) byconnecting additional Gateways 140 and application servers 120 to theLAN 122, and by adding additional local area networks. Further,additional host data centers 104 can be provided at differentgeographical locations to accommodate a wide geographic distribution ofsubscribers.

The on-line services offered to end-users of the network 100 arepreferably in the form of client-server application programs or “serviceapplications”. Each service application includes a server portion thatruns on one or more of the application servers 120, and at least onecorresponding client portion (also referred to as a “client application”or “client”) that runs on a microcomputer 102 of an end user. In thepresently preferred embodiment, the client applications are in the formof Microsoft Windows 95 executables, and the server portions areimplemented as dynamic link libraries running under the MicrosoftWindows NT operating system.

With reference to FIG. 1, the server portions of the various on-lineservices are implemented on the application servers 120 of therespective service groups 130, 132, 134. Each application server 120 ofa given service group separately runs the same server application. Forexample, each application server 120 of the Chat service group 130 runsCHAT.DLL, which is a dynamic link library that implements the serverportion of the Chat service. Similarly, each application server 120 ofthe BBS service group 134 runs a BBS dynamic link library, and eachapplication server 120 of the Dirsrv service group 132 runs a Dirsrvdynamic link library. Although each application server 120 is shown inFIG. 1 as being allocated to a single service group, a singleapplication server can simultaneously run multiple service applications,and can thus be allocated-to multiple service groups. For example, asingle application server 120 could run both the Chat and BBS dynamiclink libraries and thus be allocated to both the Chat and BBS servicegroups 130, 134.

During a typical logon session, a client microcomputer. 102 willmaintain a communications link with a single Gateway 140, but may accessmultiple on-line services (and thus communicate with multipleapplication servers 120). To initially access a service, an “open”request is generated on the client microcomputer 102 and sent to theGateway 140 that is handling the logon session. The Gateway 140 thenselects a single application server 120 (of the appropriate servicegroup) to handle the service session, and opens a pipe (e.g., a TCP/IPconnection) over the LAN 122 to the selected application server 120.

Throughout the service session, the Gateway 140 routes messages betweenthe client microcomputer 102 and the application server 120 as theclient and server portions of the service application communicate. TheGateway 140 also performs protocol translation between the protocol ofthe WAN 106 and the protocol of the LAN 122. To terminate the servicesession, a “close” request is generated on the client microcomputer 102and sent to the Gateway 140, and the Gateway 140 closes the pipe to theapplication server 120 that is handling the service session.

The architecture advantageously supports multiple simultaneous servicesessions per user. Thus, a user may be connected to multipleapplications servers (via the Gateway 140 handling the logon session)simultaneously.

Two specific on-line services, Chat and BBS, will now be brieflydescribed. This description will illustrate some of the specific typesof content entities (referred to herein as “content objects,” or simply“objects”) which may be accessed by users.

The Chat service is an interactive communications service which allowsusers to have real time conversations with other users on specifictopics. Chat conversations or “conferences” are organized as “Chatrooms” which may be entered or exited by end users to join or leave thecorresponding conferences. For example, an end user may enter a “sports”Chat room to join an interactive conversation on sports-related topics.Participants in a Chat conference can type in textual messages whichwill be displayed on the monitors of other participants. Voice and/orvideo capabilities may additionally be provided.

The BBS service allows users to post and/or review messages. Users canthereby ask and answer questions, or otherwise conduct non-real-timeconversations with other users. Although shown as a single BBS servicegroup 134 in FIG. 1, multiple BBS service groups may be formed, witheach corresponding, for example, to a particular topical area. In thepreferred implementation depicted by FIG. 1, replicated copies of allBBS content (e.g., BBS messages and folders) are stored on eachapplication server 120 of the BBS service group 134. This allows the BBSapplication servers 120 to independently process message read requestsfrom end users. Replication of BBS content is accomplished using theArbiter transaction replication service. A preferred embodiment of theArbiter service is described in commonly-assigned copending U.S.application Ser. No. 08/485,493, filed Jun. 7, 1995, having the titleTRANSACTION REPLICATION SYSTEM AND METHOD FOR SUPPORTING REPLICATEDTRANSACTION-BASED SERVICES, which is incorporated herein by reference.

With reference to FIG. 1, one of the application servers 120 of the BBSservice group 134 is preferably configured as an Internet feed server120. The BBS Internet feed server 120 reads Internet newsgroup messagesand posts these messages (by submitting update transactions to theArbiter service) within the BBS service group 134, thereby providingusers with access to such newsgroup messages. The BBS Internet feedserver 120 is also used to post messages to the Internet.

Chat rooms and BBS messages are two types of content objects that may beaccessed by users. The ability to access a given content object, and theaccess rights of the user with respect to that object, may vary fromuser to user. Using a Chat room object as an example, some users may be“participants” who can participate in the conference, while other usersmay be “viewers” who can only view the text of the conversation. One ormore users may further be designated as a “host” of the conversation. Ahost normally has the responsibility of moderating the conversation, andhas the ability to modify the access rights of members of theconversation with respect to the Chat room.

2. Overview of Directory Service and Related Components (FIGS. 1-3)

The Directory Service is an extensible on-line service that containsdatabases which describe the various content entities (i.e., the on-lineservices and associated data entities) of the network 100 that areaccessible to users. Access to these databases is provided vianavigation and edit application program interfaces (APIs) of theDirectory Service. Through these interfaces, users are provided with ahierarchical, navigable view of the various content objects available onthe network 100, and are provided with a mechanism for accessing thecontent objects.

The Directory Service is advantageously distributed among differenton-line services, which are referred to herein as “Directory ServiceProviders.” Each Directory Service Provider provides a directory to asubset of the content of the network 100. In a presently preferredimplementation described herein, the Directory Service is implemented bytwo Directory Service Providers, the Dirsrv service and the BBS service.As will be apparent from the description that follows, however, theDirectory Service supports the addition of an indefinite number of otherDirectory Service Providers. Accordingly, the preferred embodiment willbe described herein in terms of both (1) an extensible Directory Servicearchitecture which supports an indefinite number of Directory ServiceProviders, and (2) a two-Directory-Service-Provider implementation ofthe Directory service.

Each Directory Service Provider maps its content into a hierarchicaldirectory structure, which is stored within a corresponding “providernamespace.” In accordance with one aspect of the present invention, aseamless interface is provided to allow the user to transparently movefrom one directory structure to another, so that the multiple directorystructures (of the multiple Directory Service Providers) appear to theend user as a single directory structure, and so that the DirectoryService appears as a single service. This feature of the invention isdescribed in detail below.

With reference to FIG. 1, the Directory Service (abbreviated as “DS” inFIG. 1) includes the Dirsrv service (implemented on the Dirsrv servicegroup 132) and the BBS service (implemented on the BBS service group134). The Dirsrv service is the “root” of the Directory Service, andprovides users with a hierarchical, navigable view of all non-BBScontent objects (such as Chat rooms and Mediaview titles). The BBSservice provides users with a hierarchical, navigable view of all BBScontent objects.

With reference to FIG. 2, which illustrates the general organization ofcontent objects as maintained by the Directory Service, eachDirectory-service Provider maintains a respective directory structure202, 204 that represents a hierarchy of content objects. Each directorystructure 202, 204 is comprised of multiple interconnected nodes, witheach node representing a corresponding content object (or collection ofcontent objects) which may be accessed via the corresponding DirectoryService Provider. The Dirsrv directory structure 202 is stored within aDirsrv namespace 212, and is stored on the application servers 120 ofthe Dirsrv service group 132. The nodes of the Dirsrv directorystructure 202 represent the content objects which may be navigated andaccessed via the Dirsrv service. The BBS directory structure 204 isstored within a BBS namespace 214, and is stored on the applicationservers 120 of the BBS service group 134. The nodes of the BBS directorystructure 204 represent the content objects which may be navigated andaccessed via the BBS service.

The Dirsrv and BBS namespaces 212 and 214 are both provider namespaces.As described below, a seamless interface between the Dirsrv and BBSservices allows users to transparently traverse between the twodirectory structures 202, 204, so that the Directory Service appears asa single service to end users, and so that the two directory structures202, 204 are seen by users as a single tree-like directory structure.

Advantageously, additional Directory Service Providers (and additionalprovider namespaces) can be added to the Directory Service. For example,an investment service that provides data on stocks and mutual fundscould be added which acts as a Directory Service Provider with respectto its own content, and this content would be stored within a separatedirectory structure that is linked to the other directory structures202, 204. The investment service would preferably be implemented on itsown, separate group of application servers 120.

As will be apparent from the following description, the addition of newDirectory Service Providers increases the content capacity (i.e., thetotal number of nodes which can be stored) of the Directory Service. Inaddition to this ability to increase the content capacity of theDirectory Service, the capacity of a given Directory Service Provider toservice users can advantageously be increased by the addition ofapplication servers 120 to the corresponding service group.

In accordance with one aspect of the present invention, the DirectoryService is accessed via a navigation API, referred to herein as the“TreeNav” API, and via an edit API, referred to herein as the “TreeEdit”API. These APIs may be implemented in whole or in part by the differentDirectory Service Providers. As will be apparent to those skilled in theart, the provision of the TreeNav and TreeEdit APIs greatly facilitatesthe addition of new Directory Service Providers, and thereby providesfor a high degree of extensibility.

With further reference to FIG. 2, each directory structure 202, 204 mayhave thousands of nodes, and could thus represent thousands of contentobjects. The nodes can generally be thought of as “service areas” thatcan be entered by users. Links between nodes represent paths that can betaken by users in traversing the hierarchical structures 202, 204 fromone service area to another. The specific nodes and links shown in FIG.2 are provided to show the general manner in which nodes are arranged,and do not represent an existing directory structure.

In accordance with the present invention, the Directory ServiceProviders are free to use any database arrangement for the storage oftheir respective nodes. In the preferred embodiment, the DirectoryService Providers store their respective nodes as node files of afilesystem, with each node file containing a list of node propertiesthat represents a single node. Various other database arrangements arepossible. For example, a Directory Service Provider could be configuredto store its nodes within an SQL (Structured Query Language) database.

The hierarchical directory structures 202, 204 are preferably in theform of directed acyclic graphs. As is well known in the art of filesystems, a directed acyclic graph structure is more flexible than astrict tree structure, since a directed acyclic graph allows a node tohave multiple parent nodes. (A “parent” of a given node is any node thatis both (1) directly connected to the given node, and (2) at a higherlevel in the hierarchy than the given node. Similarly, a “child” is anynode that is both (1) directly connected to the given node, and (2) at alower level than the given node.) This characteristic of the directorystructures 202 and 204 is illustrated by nodes 7 and 13, each of whichhas two parent nodes. In other embodiments of the invention, a stricttree structure may be used.

With reference to FIG. 2, the extensible, composite structure 220 formedby the two directory structures 202 and 204 (and other directorystructures which may be added) will be referred to herein as the“content tree.” This use of the term “tree,” however, is not intended tosuggest that the composite structure 220 is a strict tree structure.

As will be appreciated by those skilled in the art, the provision formultiple Directory Service Providers that are seamlessly linked to oneanother advantageously allows the task of providing a directory serviceto be distributed among multiple, different services. This isparticularly advantageous when the volume of the content on the network100 is sufficiently high such that a single service cannot efficientlystore and provide access to all node. Conversely, the ability todistribute the Directory Service among a variable number of servicesenables the content tree 220 to be expanded (by the addition of newnodes) without a corresponding degradation of performance.

As will further be appreciated, because different Directory ServiceProviders store and provide access to different types of nodes, eachDirectory Service Provider can be tailored to the specific requirementsof the type or types of nodes stored by that Directory Service Provider,without concern for the specific requirements of other types of node. Byway of specific example, only the BBS service needs to include code formonitoring and deleting old BBS message nodes, since the BBS service isthe only Directory Service Provider that stores BBS message nodes. Thisfeature of the present invention will be apparent from the descriptionthat follows.

In the preferred embodiment, the content tree 220 is displayed to theend user via a network shell application which runs on the clientmicrocomputers 102 of end users. The network shell is the primary clientof the Directory Service. A preferred implementation of the networkshell is described in a commonly-assigned U.S. application having thetitle ON-LINE NETWORK ACCESS SYSTEM, filed Jul. 17, 1995, which isincorporated herein by reference. In the preferred embodiment, thenetwork shell is an integral part of the Microsoft Windows 95 Explorerprogram (hereinafter “the Explorer”), which is described in InsideWindows 95, Microsoft Press, 1994. As will be apparent to those skilledin the art, other types of shell applications could be used. Asdescribed below, a graphical user interface of the Explorer displays thecontent objects as a logical extension of the user's hard drive, withnodes represented by corresponding icons on the user's screen.

In accordance with the present invention, the content tree 220 includesthree different types of nodes: leaves, folders and junction points. Aset of flags stored in association with each node identifies the node asone of these three types. Leaves (or “leaf nodes”) are nodes that both(1) cannot have children and (2) do not serve as junction points. Theleaf nodes in FIG. 2 are nodes 4-7, 12 and 13 (assuming that these nodescannot have children). Leaves represent the actual services withinnetwork 100. Examples of leaves include Chat rooms, BBS messages,Mediaview titles and download-and-run files. When the user clicks on aleaf node (by double clicking on the double corresponding icon from awindow of the Explorer), the corresponding service-related action istaken. For example, if the user double clicks on a Chat room icon, theChat service is opened and the user is added to the corresponding Chatconference. When the user double clicks on an icon for adownload-and-run file, the file is downloaded to the user's computer102.

Folders are nodes that both (1) can have children, and (2) do not serveas junction points. The folder nodes in FIG. 2 are nodes 0-3 and 9-11.Folder nodes normally represent collections of other content objects,and are used to organize the content of the network. For example, afolder node may correspond to a BBS folder on a particular topic, or mayrepresent a collection of BBS folders and Chat rooms on a related topic.Folder nodes are also used to generally arrange content objectsaccording to language. For example, node 1 may be an english foldercontaining content objects that are primarily in english, and node 2 maybe a spanish folder containing content objects that are primarily inspanish. Folder nodes are generally analogous to the directories of afile system.

Junction points are nodes that serve as proxies for nodes in otherprovider namespaces and that allow the user to seamlessly traversebetween provider namespaces. The only junction point shown in FIG. 2 isnode 8, which serves as a proxy for BBS folder node 10 (referred to asthe “target node”). When, for example, the user double clicks on node 8,the Explorer launches a BBS navigator and shows the user the children ofnode 10. Although only a single junction point is shown in FIG. 2, manyjunction points may be provided within the content tree 220. Junctionpoints are discussed in detail below under the heading JUNCTION POINTS.

With reference to FIG. 3, a graphical user interface of the Explorerdisplays the content tree 220 as a logical extension of the user's harddrive. In the window configuration shown, the left-hand window pane 302displays a hierarchical map 304 of folder nodes, and the right-handwindow pane 308 displays the icons 310 and names 312 of the contentobjects within a selected folder node. The hierarchical map 304corresponds to a portion of the content tree 220. In the example shownin FIG. 3, the map 304 includes three folder nodes with names of“categories (US),” “Member Assistance (US),” and “Favorite Places,” andthe right-hand window pane 304 displays the contents of the “Categories”folder (which has been selected by the user from the left-hand pane302).

Using the Explorer, users can browse the content tree 220 and can accessthe various content objects. Various actions are available to the userto reveal different levels of nodes. For example, the user can click ona folder displayed in the left pane 302 to “expand” the folder, or canclick on a “parent folder” button (not shown) to move upward through thecontent tree. To access a content object (to, for example, enter aspecific on-line service), the user can double click on the icon forthat object. Because the content tree 220 is preferably structured as anacyclic graph, the user may take different paths to get to the samecontent object. The particular actions which can be performed by a userupon accessing a node depend upon the user's access rights with respectto the node, which are stored within the access rights databases 152 onthe security servers 150. Access rights of users can advantageously bespecified within the database on a single-user basis.

In accordance with one aspect of the present invention, the DirectoryService only “shows” to each user those nodes that the user isauthorized to access, or equivalently, those nodes to which the user hasaccess rights. (In the preferred embodiment, the lowest level of accessrights a user can have at a node is “viewer-only.” A user withviewer-only level access rights at a node can view-certain properties ofthe node, but cannot either modify the properties or open thecorresponding service.) Thus, each user is provided with a filtered viewof the actual content of the network 100, seeing only the icons of thenodes that the user is authorized to view or otherwise access.

This feature of the invention advantageously allows certain nodes andcontent objects to be completely hidden from certain classes of users.For example, this feature may be used to hide from the view of regularusers a BBS folder (and its contents) that has been created for privatecorrespondence between members of a family, so that the only users whocan see the folder from the Explorer are the designated family members.Because only those authorized to access each node can see the node, ahigh degree of security is provided against unathorized accesses.

In the preferred embodiment, a Sysop Tools client application (which ispreferably integrated with the Explorer) allows authorized end users toremotely edit the content tree 220. Edits to the content tree can alsobe made locally (i.e., from within the host data center 104) by systemadministrators. Edits to the content tree 220 are made via the methodsof the TreeEdit API, which are implemented by the various DirectoryService Providers. These methods include methods for adding and deletingnodes, and for editing the properties of existing nodes. The capabilityof a user to edit the content tree 220 is specified by the user's accessrights. To determine the access rights of users, the Directory ServiceProviders generate user-specific queries of the access rights database152 (using a GetAccountRights API, as described below under the headingLOCALES AND ACCESS RIGHTS FILTERING OF NODES).

Users that have the capability to edit the content tree 220 aregenerally referred to as “sysops,” although different levels of sysopsare defined. Advantageously, different users can have different editcapabilities with respect to different nodes. For example, one user mayhave node edit privileges (or “sysop privileges”) only at a particularDirsrv folder node (plus any children of the Dirsrv folder node), whileanother user may have node edit privileges only at a particular BBSfolder node (plus any children of the BBS folder node).

As a user moves from node to node of the content tree 220 using theExplorer, the Explorer requests the node-specific access rights of theuser from the Directory Service. If these access rights indicate thatthe user has sysop privileges at a particular node, the Exploreradvantageously displays a set of node edit menu items, allowing the userto remotely edit the properties of the node using the TreeEdit API. Apreferred set of tools for remotely editing the content tree 220 isdescribed in a concurrently filed, commonly assigned U.S. applicationhaving the title SYSTEM AND METHOD FOR EDITING CONTENT IN AN ON-LINENETWORK, which is incorporated herein by reference.

As pictorially illustrated in FIG. 1, the Dirsrv directory structure 202is stored on each of the application servers 120 of the Dirsrv servicegroup 132. Similarly, the BBS directory structure 204 is stored on eachof the application servers 120 of the BBS service group 134.Accordingly, any single application server 120 within the Dirsrv servicegroup 132 can provide a directory of all of the nodes within the Dirsrvnamespace 212, and any single application server 120 within the BBSservice group 134 can provide a directory of all of the nodes within theBBS namespace 214. As with other service groups within the host datacenter 104, each service group 132, 134 may have as few as oneapplication server 120.

As indicated above, the Directory Service Providers may store theirrespective nodes as node files, or may use an alternative databasearrangement. In the preferred embodiment, each node includes a listingof the parents and children of the respective node, and therebyspecifies the position of the node within the content tree 220. Withreference to FIG. 2, each node also includes a variable-length list ofnode properties, as illustratively shown for node 4. These nodeproperties essentially define the corresponding content object (or“service area”), and specify how the content object may be accessed.

The node properties stored by the Directory Service Providers varyaccording to node type. For example, some properties are applicable onlyto folder nodes, some are applicable only to leaf nodes, and some areapplicable to both leaf and folder nodes. Further, some properties areservice-specific, meaning that they apply only to a certain service. Anexample of a service-specific property is a Chat room “maximumoccupancy” property, which specifies the maximum number of users thatcan concurrently participate in a corresponding Chat conference.Further, some properties can be viewed by regular users (i.e.,non-sysops) via a properties dialog box of the Explorer, while otherproperties are hidden from regular users, and can be seen only by sysopsand/or system administrators.

In accordance with the present invention, a set of generic (i.e.,non-service-specific) properties is defined to allow Directory ServiceProviders to store certain types of information. The mnemonic names anddescriptions of these generic properties are provided below. Provided inparenthesis following each name and description is a list of codes whichidentify certain characteristics of each generic property. These codesare defined in Table 1. TABLE 1 CODE MEANING V/NV Property is/is notvisible to users via the properties dialog box of the Explorer FProperty applies to folder nodes L Property applies to leaf nodes

The generic properties are as follows:

Name. This is a human readable name, which can be displayed by a client(i.e., client application) of the Directory Service. For example, afolder node could have the name “Health & Fitness,” and could havechildren folder nodes with names of “Health & Fitness Chat” and “Health& Fitness BBS.” Every folder node and every leaf node has a name. Forjunction point nodes, the name of the target node is used (i.e., theproperty is stored remotely as a local property of the target node). Inthe preferred embodiment, the Explorer (which, as indicated above, isthe primary client of the Directory Service) displays the name alongwith or in place of the corresponding icon. (V, F, L). Directory EntryID (DEID). This is a 64-bit number which uniquely identifies a nodewithin its respective provider namespace. (A provider namespace can thushave up to 264 nodes.) Every node has a DEID. (NV, F, L).

Application ID (APPID). This is a 32-bit number that is required ofevery node. For leaf nodes, this number identifies the clientapplication associated with the node, and is used by the Explorer tolaunch this client application when the user double-clicks on the node.(The client application then opens a pipe to the associated service.)For folder nodes, the APPID indicates the provider namespace (e.g.,Dirsrv or BBS) in which the node resides. (The Directory Service canthus support up to 2³² different namespaces.) For junction point nodes,the APPID indicates the provider namespace in which the target noderesides. (NV, F, L)

Service Group ID. (Also referred to as the data set ID, or “Dset”.) Thisis a 16-bit number which identifies the service group (132, 134, etc.)of the Directory Service Provider in which the node resides. Every nodehas a service group ID. Each Directory Service node is uniquelyidentified globally by the combination of the node's DEID, APPID andService Group ID. (NV, F, L). Icon ID. This is a 32-bit number (in theform of a “shabby ID,” as described below) which identifies the icon tobe displayed by the Explorer (or other client) as a representation ofthe node. Icon bitmaps are stored by the Directory Service, and are sentover the network upon request by the Explorer. Multiple nodes may havethe same icon. (NV, F, L). Flags. This is an 8-bit value which indicateswhether the node is a folder, leaf, or junction point. Every node hasthe Flags property. (NV, F, L).

Security Token. This is a 32-bit value which identifies a contentcategory to which the node has been assigned for security (i.e., accessrights) purposes. When a user attempts to view or access a node, thenode's security token and the user's 32-bit account number are used todetermine the user's access rights with respect to the node. Everyfolder node and every leaf node has a security token. For junction pointnodes, the security token of the target node is used. (NV, F, L).

Description. This is a human-readable textual description of the servicearea corresponding to the node. The Directory Service places nolimitation on the length of the description. (V, F, L).

GoWord. This is an optional property of nodes in provider namespacesthat support GoWord searches. GoWords are in the form of characterstrings. If a Directory Service Provider supports GoWord searches, thenthe GetDeidFromGoword API (discussed below) can be used to retrieve theDEID of the node with a particular GoWord, and the node can then bedirectly accessed (assuming the user is authorized to access the node).Two nodes within the same provider namespace cannot have the sameGoWord. (V, F, L).

Search Keywords. These are search words which may optionally bespecified by sysops to permit keyword searching for nodes on particulartopical areas. Multiple search keywords may be specified for a singlenode. The search keywords are cross-referenced to the corresponding nodeby a “find” service. (V, L, F).

Owner. This is a 32-bit vendor ID which identifies the entity whichprovides or derives revenue from the corresponding service. (V, F, L).

Sysops. These are the names of the users that are sysops of the node.(V, F, L).

Pricing. This is a 32-bit value which indicates the cost to the user, ifany, associated with accessing the corresponding service area. Forexample, the pricing property of a node for a Chat room specify a costto the user of $1.50 per use, or $2 per hour. The general format of thepricing property is described below. (V, F, L).

Rating. This is a 32-bit value which specifies a suggested appropriateaudience for the content which corresponds to the node. Ratings include“GA: General Audiences,” “MA-13: Mature Audiences,” and “AO: AdultsOnly.” (V, F, L)

Run Info. This is a localized string containing miscellaneous run-timeinformation needed (for certain nodes) to start or open a pipe to aservice. For example, the property could contain a filename or othermoniker that specifies a file on an application server 120. (NV, L).

Locales. This optional property is in the form of a string of localesidentifiers (“LCIDs”) that identify the locales (i.e., languages and/orgeographic regions) to which the node has been customized (or in whichthe node is viewable). For example, the locales property of a node thatincludes a textual description (or audio narration) that is in spanishmay have only the LCID for “spanish” (which may be set by a sysop whocreates the node); the locales property of a node for a rock music audioclip may include the LCIDs of many different languages and/or regions.In one embodiment, the locales property may be used to specify ageographic region to which the content object applies. Thus, forexample, the locales property of a “classified ads” BBS node that isdirected to residents of Daytona Beach Fla. may have the LCID forDaytona Beach. As described below, the Directory Service provides amechanism for allowing the client to specify the locales that the useris interested in, and for filtering out any nodes that are not in any ofthe user-specified locales. This advantageously prevents the unnecessarydownloading and viewing of nodes in which the user has no interest. (V,F, L).

Junction. For junction point nodes, this is the DEID of the target node.(NV).

Parents. This is the number of parents of the node. The DirectoryService determines this number on-the-fly (rather than storing thenumber) upon request from the client. (NV, F, L).

Children. This is the number of children of the node. The DirectoryService determines this number on-the-fly (rather than storing thenumber) upon request from the client. (NV, F).

Access Rights. This is a sixteen bit value, retrieved by the DirectoryService from an access rights database 152, which specifies the accessrights of a particular user at the node. Each defined bit of this valueserves as a privilege level flag for indicating whether or not the userhas a particular privilege level at the node. In the preferredembodiment, the user can have one or more of the following privilegelevels: viewer, observer, user, host, sysop, sysop manager, supersysop.Although the access rights value is technically not a property of thenode (since the value may vary from user to user), it is made availableto the client by the Directory Service as a node property. (NV, F, L).

Soundfile ID. This is a 32-bit number (in the form of a shabby ID, asdescribed below) which identifies a sound file that corresponds to thenode. The various sound files are stored by the Directory Serviceseparate from the node properties, and are provided to the client uponrequest. Each sound file specifies a corresponding sound or set ofsounds that may be generated by the client microcomputer 102 when theuser accesses the node. (NV, F).

Banner ID. This is a 32-bit number (in the form of a shabby ID, asdescribed below) which identifies a banner object for providing afolder-specific banner within the right window pane 308 of the Explorerwhen the user opens a folder. Various graphics formats for specifyingbanners are supported, including bitmaps and various metafile formats.(A metafile is a standard Microsoft Windows graphics object thatconsists of lists of primitive graphics commands.) Banner objects arestored by the Directory Service separate from the node-properties, andare provided to the client upon request. (NV, F).

Drfile ID. (Download-and-run file ID). This is a 32-bit number (in theform of a shabby ID, as described below) which identifies adownload-and-run file for the node. In the preferred embodiment,download-and-run files are small files (usually less than 5 kilobytes)that sysops can place in their folders to provide information (such asinformation on the standards of on-line conduct) to users. The variousdownload-and-run files are stored by the Directory Service separate fromthe node properties, and are provided to the client upon request. (NV,L).

Throughout this detailed description, the first letter of each of theabove-listed mnemonic property names is capitalized to emphasize thatthese names correspond to defined properties. Further, acronyms (such asDEID, and APPID) of mnemonic property names will be fully capitalized.

In addition to the properties listed above, various other genericproperties are possible. For example, generic properties may be includedto specify the creation date of the node, the date/time of the lastmodification to the node, the time frame (e.g., 12th-century) to whichthe content of the node relates, the version of the node, or the DEIDsof other nodes to which the present node is related.

As indicated by the foregoing, the only properties that are required ofall nodes in the preferred embodiment are the DEID, APPID, Service GroupID and Flags properties. The Name and Security Token properties arerequired of all leaf and folder nodes, and the Junction property isrequired of all junction point nodes. The remaining properties areoptional, meaning that they may or may not be specified (depending uponthe particular service with which the node is associated). As describedbelow, a set of node editors are provided to inform the Explorer, foreach service, of the properties which may be entered by sysops for thenodes of that service. These node editors also allow nodes to haveservice-specific properties, such as the above-mentioned maximumoccupancy property. Typically, the set of properties that may bespecified for a given node type (such as Chat room leaf nodes, or BBSfolder nodes) includes a subset of the above-listed generic properties,and may include one or more service-specific properties.

As will be recognized from the foregoing, each node is simply a list ofproperties stored by or otherwise available via the Directory Service.This list of properties describes the corresponding service area (orcontent object) on the network, and in the case of leaf nodes, providesthe information needed to enter the service area. By way of example, theproperty list for a Chat room node (which is one type of leaf node) willtypically include user-readable information about the Chat room, andwill include the information needed by the Explorer to launch the Chatclient application and add the user to the Chat room.

The Directory Service operates generally as follows. In response torequests from the client (which, in the preferred embodiment, is theExplorer), the Directory Service sends node properties over the WAN 106to the client microcomputer 102, allowing the client to reconstructuser-selected portions of the content tree 220 (as shown in FIG. 3 forthe Explorer) on the user's screen, and/or allowing the client todisplay node properties (such as the GoWord for the node) to the enduser. To avoid unnecessary transfers of information over the WAN 106,the Directory Service advantageously returns only those properties thatare specifically requested by the client.

Assuming that the Explorer is used as the client, when the user doubleclicks on a folder node (i.e., the icon for the folder node) from theright pane 304, or expands a node in the left pane 302, the Exploreruses a GetChildren API to generate a request to the Directory Servicefor the children of the folder node, specifying as parameters of the APIthe DEID of the folder node plus the names of the specific propertiesneeded to display the children of the folder node. (The specificproperties requested by the Explorer with such GetChildren calls arehard coded into the Explorer. In a preferred embodiment, the requestedproperties are the DEID, APPID, Name, Flags, Icon ID, Service Group ID,and the user's Access Rights.)

Various user actions cause the Explorer to generate requests fordifferent node properties. For example, from the Explorer, a user canselect a node and then select the “properties” command; this causes theExplorer to open the “properties” dialog box, which allows the user toselect a “properties sheet” which lists the properties to be retrievedby the Explorer. The user may then specify, for example, “general”properties sheet which includes the “Rating” and “Pricing” properties ofthe node, causing the Explorer to generate a request for theseproperties. The TreeNav methods used by the Explorer for requestingproperties and other information from the Directory Service aredescribed below.

When the user double clicks on a leaf node from the Explorer, theExplorer initiates a service session with the corresponding service. Toinitiate the service session, the Explorer initially uses the APPID ofthe leaf node to identify the service application to be invoked. Oncethe identity of the appropriate executable file has been determined, theExplorer launches the client application for the service, and passes tothe client application the DEID and the service group ID of the node.The client application then performs the appropriate service-relatedaction. For example, if the node is a Chat room, the Chat clientapplication uses the node's DEID to connect to the corresponding Chatroom.

Before “showing” a node to the end user (by returning the requestedproperties of the node to the client), the Directory Service uses aGetAccountRights API to determine the access rights of the user withrespect to the node to thereby determine whether the user is authorizedto access the node. This access rights information is stored within theaccess rights database 152 on each security server 150. If the user isnot authorized to access the node, the Directory Service does not returnthe properties of the node, and the node is not displayed to the user.By way of example, suppose that a user double clicks on the iconcorresponding to node 1 in FIG. 2. This causes the Explorer to generatea GetChildren call to the Directory Service to obtain the children(i.e., enumerated properties of the children) of node 1. As parametersof the GetChildren request, the Explorer specifies the DEID of node 1,and specifies the properties (normally the Name, DEID, APPID, ServiceGroup ID, Flags, Icon ID and Access Rights) to be returned for eachchild node. If, for example, the user is authorized to access node 4,but is not authorized to access node 5, the Directory Service willreturn only the properties of node 4. Thus, no properties of node 5 willbe downloaded to the Explorer, and node 5 will not appear in theExplorer window on the user's screen.

To determine the user's access rights with respect to the node, theDirectory Service initially reads the 32-bit Security Token associatedwith the node (which, as described above, is stored as a node property).The Directory Service then generates a GetAccountRights call, specifyingas parameters of the call the node's Security Token and the user's32-bit account number. The GetAccountRights API returns either a 16-bitaccess rights value which indicates the user's-access rights withrespect to the node, or else returns a code indicating that the user isnot authorized to access the node. The GetAccountRights API includescode which generates queries to the access rights databases 152 toobtain user-specific access rights lists, and also includes code whichimplements an access rights cache for locally storing theseuser-specific lists. The GetAccountRights API is further describedbelow.

With the exception of the Access Rights property, which is a specialcase, all of the above-listed generic properties are “local properties,”meaning that they are stored (or generated on-the-fly) locally (i.e., onthe same application server 120) by the Directory Service Provider whichstores the node. In accordance with one aspect of the present invention,a node may also have one or more “remote properties,” which areproperties that are stored or generated by the service (such as Chat)with which the node is associated (as indicated by the node's APPID).When a remote property is requested by the client, the Directory ServiceProvider retrieves the remote property (via a remote procedure call, or“RPC”) from the associated service (which is normally implemented on aseparate application server 120), and then returns the remote propertyto the client. To increase performance, the Directory Service alsoimplements a remote properties cache (described below) for locallycaching recently-retrieved remote properties. As described below underthe heading “JUNCTION POINTS”, the Name and Security Token properties ofa junction point node are always stored remotely by the DirectoryService Provider that stores the corresponding target node.

The provision for the retrieval of remote properties advantageouslyallows certain types of information to be stored or generated by the endservices (such as Chat or Mediaview), rather than by the DirectoryService Providers. This is particularly useful for information thatchanges dynamically. One example of a node property which mayadvantageously be stored remotely is a “Current Occupants” property of aChat room, which indicates the current number of participants in thecorresponding Chat conference. Because the Current Occupants propertychanges frequently, it would be inefficient to store this property withthe node; doing so would require frequent update transactions over theLAN 122.

In accordance with one aspect of the present invention, a mechanism isprovided which allows Directory Service Providers to maintain respectivedatabases of data entities that are shared by multiple nodes. Theseshared data entities are referred herein as shared blocks of bytes, or“shabbiest” In the presently preferred embodiment, four types of dataentities are stored as shabbies: icon bitmaps, download-and-run files,sound files, and banner objects. As illustrated in FIG. 2 for onepreferred embodiment, only the Dirsrv service implements a shabbydatabase 222. Each shabby within the database 222 is specified by aunique 32-bit shabby ID (“SHID”).

The ability for a Directory Service Provider to maintain a database ofshabbies separate from the nodes of the Directory Service Provider isprovided through special TreeNav and TreeEdit methods that may be usedto create, delete, modify and download shabbies, and by the provision ofcertain node properties (such as the “Icon ID” property) that allowspecific shabbies to be referenced by nodes. Because shabbies are storedseparately from the node properties, there is no need to store multiplecopies of each shabby, even though multiple nodes may share the sameshabby. By way of example, suppose that the same icon is used for allChat rooms, and that 30 Chat room objects currently exist within theDirsrv namespace 212. Rather than storing 30 copies of the bitmap forthe Chat room icon, the Dirsrv service stores the bitmap as a shabby(within the Dirsrv shabby database 222), and stores the shabby ID of thebitmap as the Icon ID property each Chat room node. The preferredmethods by which shabbies are stored by Directory Service Providers—anddownloaded to client computers 102 are described below under the heading“SHABBIES.”

3. Client-Server Architecture of Directory Service (FIG. 4)

FIG. 4 illustrates the primary client and server software componentswhich may be invoked when a user uses the Explorer client application402 to explore and/or edit the content tree 220, and also illustratesthe primary data entities accessed by these software components.

The client components include the Explorer client application 402, avariety of other client applications 404 (such as the clientapplications for the Chat, BBS and Mediaview services), the TreeNav API412, the TreeEdit API 414 (which, as discussed below, may be omitted inembodiments which do not allow remote editing of the content tree 220),and network layers 416. The server components include network layers418, the Dirsrv and BBS server applications 420, 422 (which are bothDirectory Service Providers, and which together form the DirectoryService 424), and various other server applications 426 (such as theChat and Mediaview service applications). The Directory Service 424accesses the Dirsrv and BBS namespaces 212, 214, and may accessadditional provider namespaces 438 that correspond to other DirectoryService Providers (represented by the ellipsis in FIG. 4).

The Explorer 402 includes multiple navigator modules 440 for navigatingthe content tree 220. Each navigator module 440 corresponds to and isused to navigate a respective provider namespace 212, 214, 438. Thus,for example, a Dirsrv navigator module is provided to navigate theDirsrv namespace 212, and a BBS navigator module is provided to navigatethe BBS namespace 214. Each navigator module 440 is preferablyimplemented as a dynamic link library (DLL) which is invoked by theExplorer 402 when the user enters into the corresponding providernamespace 212, 214, 438. With reference to FIG. 2, for example, when theuser double clicks on the icon for junction point node 8, the Explorer402 launches the BBS navigator to allow the user to navigate the BBSdirectory structure 204.

With further reference to FIG. 4, the navigator modules 440 use theTreeNav API 412 to navigate the content tree 220. The TreeNav API 412provides all of the functionality for navigating and extractinginformation from the Directory Service Providers 420, 422, and includesthe following methods:

GetProperties. Retrieves specific properties of a list of known nodes.The properties to be retrieved and the list of nodes are specified asparameters of the method.

GetParents. Retrieves specific properties of the parents of a knownnode. The properties to be retrieved and the identity (DEID) of theknown node are specified as parameters of the method.

GetChildren. Retrieves specific properties of the children of a knownnode. The properties to be retrieved and the identity (DEID) of theknown node are specified as parameters of the method.

GetDeidFromGoWord. Retrieves the DEID of the node that has the specifiedGoWord.

GetShabby. Gets a specific shabby given its shabby ID (SHID).

EnumShn. (“Enumerate shabby number”). Returns a listing of all shabbynumbers given a shabby kind.

The TreeNav methods are further described below under the headingTREENAV METHODS.

With further reference to FIG. 4, the Explorer 402 also includes anoptional Sysop tools client application 444, which may be invoked aspart of the Explorer when a user has sysop-level privileges at a givennode. The Sysop tools client application 444 generates calls to theclient side of the TreeEdit API 414. The TreeEdit API 414 provides thefunctionality for modifying the content maintained by the DirectoryService Providers, and consists of the following methods:

AddNode. Adds a node to the content tree 220.

DeleteNode. Deletes a node from the content tree 220.

SetProperties. Adds, deletes and/or modifies the properties of a node.Properties are deleted by specifying a property type of “sptNil” (Table2 below) and a property size-of zero.

GetStatus. Returns the current status of a transaction.

Lock. Locks a provider namespace, to thereby prevent TreeEdit operationsby anyone other than the locker.

Unlock. Unlocks a locked provider namespace.

LinkNode. Links two nodes, making one the child of the other.

UnlinkNode. Unlinks two nodes, provided that an orphan node does notresult.

AddShabby. Adds a shabby.

DeleteShabby. Deletes a specified shabby.

ChangeShabby. Modifies an existing shabby.

OrderChildren. Sets the order of the children of a specified node.

As described above, the capability of a given user to edit the contenttree 220 using the TreeEdit methods depends upon the particular accessrights of the user, which are specified within the access rightsdatabase 152. These access rights are determined by the DirectoryService Providers by generating GetAccountRights calls, and are passedacross the network (via the TreeNav methods) to the Explorer 402. If,for example, a user has sysop-level privileges at a given node, theSysop Tools client application 444 will display the node edit menu items(within the Explorer window) to the user, allowing the user to invokecertain of the TreeEdit methods to edit the properties of the node.

Each Directory Service Provider 420, 422 supports at least a subset ofthe TreeNav and TreeEdit methods, depending upon the level of DirectoryService functionality provided. In the preferred implementation, theDirsrv service supports all of the TreeNav and TreeEdit methods, and theBBS service supports all TreeNav and TreeEdit methods except for theshabby and Goword methods. (The BBS service thus does not support GoWordsearches, and does not support the use of shabbies). Calls to methodsthat are not supported by a Directory Service Provider return an errorcode.

Advantageously, the TreeNav and TreeEdit interfaces provide anextensible framework for the addition of new Directory ServiceProviders. To add a Directory Service Provider, a server application isadded which supports at least a subset of the TreeNav and TreeEdit APIs,and a corresponding navigator module 440 is added on the client sidewhich generates TreeNav calls to the new server application. Once abasic set of folder nodes has been created within the provider namespaceof the newly-added Directory Service Provider, junction points can beadded to the new provider namespace (and to other provider namespaces)to create links to existing Directory Service Providers.

As will be apparent from the foregoing, each Directory Service Provideradheres in whole or in part to a “Directory Service standard” whichessentially ties together the various Directory Service Providers toform a single, integrated DS. This standard is generally defined by (1)the methods of the TreeNav and TreeEdit APIs, (2) the three types ofnodes (and their corresponding definitions) which may be stored byDirectory Service Providers, and (3) the predefined properties (bothoptional and mandatory) which are stored by the Directory ServiceProviders. Although every Directory Service Provider must follow thisstandard at least in-part, various aspects of the Directory ServiceProviders are left open to developers. For example, the DS standard doesnot require any specific database implementation for the storage ofnodes, and does not limit the types of properties which may be stored bythe Directory Service Providers.

With further reference to FIG. 4, the Explorer 402 also includesmultiple node editors (NEDs) 442. Each node editor 442 corresponds to arespective service on the network 100, and specifies a set of nodeproperties that may be entered (by sysops) for nodes that correspond tothat service. For example, a node editor 442 for the Chat servicespecifies the properties which may be entered for Chat room nodes (whichare one type of leaf node), and a node editor for the Dirsrv servicespecifies the properties that may be entered for Dirsrv nodes (which arethe folder nodes within the Dirsrv namespace).

Each node editor 442 is preferably in the form of a separate dynamiclink library. When a new service is added to the network 100, acorresponding node editor 442 is simply downloaded to the clientmicrocomputer 102 to allow sysops to create and edit Directory Servicenodes for the new service.

The node editors 442 advantageously provide a mechanism for allowing theproperties of Directory Service nodes to be customized on a per-servicebasis, and allow service-specific properties to be defined for nodes.When, for example, a new node is remotely created (or edited) by asysop, the corresponding node editor 442 is invoked to provide aproperty sheet of the properties that can be set by sysops. (Certainproperties, such as the DEID, APPID, and service group ID are setautomatically, and cannot be modified by regular sysops). The sysop canthen specify or modify these properties via a user interface of theSysop Tools client application 444. The specific properties which may bemodified by the user depend upon the sysop level (e.g., regular sysop,sysop manager, supersysop, etc.) of the user at the node.

As will be recognized from the forgoing, the Sysop Tools clientapplication 444 and the TreeEdit API 414 are provided for the purpose ofallowing sysops to remotely edit the content tree, and are not invokedunless the user has sysop privileges. Accordingly, these components mayoptionally be omitted in copies of the Explorer 402 code that areprovided to regular (non-sysop) users.

A preferred implementation of the Sysop Tools client application 444,the TreeEdit API 414 and the node editors 442 is described in theabove-referenced application of the title SYSTEM AND METHOD FOR EDITINGCONTENT IN AN ON-LINE NETWORK.

With further reference to FIG. 4, the Explorer 402 also includes codefor implementing a non-persistent node cache 450. During each logonsession the Explorer 402 stores node properties that are returned by theDirectory Service in the node cache 450. Before requesting theproperties of a node, the Explorer 402 checks the node cache 450 to seeif the properties have already been returned. Unnecessary transfers ofproperty data are thereby avoided. At the end of each logon session, thenode cache 450 is flushed, so that the reconstructed content tree 220seen by the user upon the following logon session will reflect anychanges that are made to the content tree 220.

The Explorer 402 also maintains a shabby cache 452 for storing certaintypes of shabbies that are returned by the Directory Service 424. In thepreferred embodiment, the Explorer 402 stores icon bitmaps, sound filesand banner objects within the shabby cache 452. The shabby cache 452 ispreferably implemented on the hard disk of the user's microcomputer 102as a persistent cache.

When the Directory Service 424 needs a shabby (such as an icon bitmap)for a node, the Explorer 402 initially requests the correspondingproperty (e.g., Icon ID, Soundfile ID, or Banner ID) of the node fromthe Directory Service, or, if the property has already been returned,reads the property from the node cache 450. Once the property (i.e.,shabby ID) has been obtained, the Explorer 402 checks the shabby cache452 for the corresponding shabby. If the shabby is not present in theshabby cache 452, the Explorer 402 generates a GetShabby call to theDirectory Service Provider of the node (assuming the Directory ServiceProvider supports shabbies), specifying the shabby ID as a parameter ofthe GetShabby API. (As described below, download-and-run file shabbiesare preferably returned using the FTM service, rather than the GetShabbyAPI.)

In the preferred embodiment, each time the Directory Service 424 returnsa shabby that is an icon bitmap, sound file or banner object, the shabbyis stored in the shabby cache 452 in association with its shabby ID(SHID). Because these shabbies are stored in the cache 452 inassociation with their shabby IDs, rather than in association with thenodes to which they correspond, duplicate copies of shabbies within theshabby cache 452 are avoided.

Advantageously, the contents of the shabby cache 452 are not flushedbetween logon sessions. Thus, once an icon bitmap, sound file, or bannerobject has been returned by the Directory Service, it need not bere-transferred over the WAN 106 on subsequent logon sessions. Duplicatetransfers of these kinds of shabbies are thereby avoided. To avoid largevolumes of shabby data on the user's hard disk, a conventionalleast-recently-used (LRU) algorithm or similar algorithm may be used todelete from the shabby cache 452 any shabbies that have not recentlybeen read from the cache 452.

4. Representation of Node Properties (FIG. 5)

With reference to FIG. 5, each node of the content tree 220 can beviewed as a table 500 of node properties to which the Directory Serviceprovides access. This table 500 includes at least a subset of theabove-listed generic properties (which includes the DEID, APPID ServiceGroup ID, Flag, Security Token and Name of the node), and may alsoinclude one or more service-specific properties (such as a “maximumlength of conversation” property for a Chat room).

At least some of the properties in the table 500 are local propertiesthat are stored (or for some properties, generated on-the-fly) locallyby the Directory Service Provider that provides access to the node. Inthe preferred embodiment, node files are used to store the localproperties. The table 500 may also include one or more remote properties(which may be either generic or service-specific in nature) that arestored or generated on-the-fly by a separate (or “remote”) service. Thisseparate service is the service to which the node corresponds (such asChat, BBS, Dirsrv or Mediaview), as indicated by the node's APPID.

Each node property, whether local or remote, has a property name 502, aproperty type 504, and a property value 506. Each property name 502 ispreferably in the form of a null-terminated sequence of bytes whichuniquely identifies a corresponding property. Property names 502 arepassed over the WAN 106 whenever a TreeNav or TreeEdit API call requiresthe identification of one or more properties. To maintain highperformance over the WAN 106, the most commonly requested properties areprovided with very short names (typically 2 or 3 bytes long, includingthe terminating null). For example, the DEID, Flags, and APPIDproperties have null-terminated string names of “a”, “b”, and “c”,respectively. (Longer, mnemonic names such as “szPropDeid,”“szPropFlags,” and “szPropAppid” are used by programmers to identify theproperties, and these mnemonic names are converted into the actualproperty names 502 by the compiler.) The “type” 504 of a propertyidentifies the data format (e.g., byte, word, doubleword, characterstring, etc.) of the corresponding property value 506. Properties canhave any of the types listed in Table 2. TABLE 2 TYPE NUMERIC (MNEMONICNAME) IDENTIFIER DESCRIPTION sptNil 00H invalid sptByte 01H unsignedbyte sptWord 02H unsigned word sptDword 03H unsigned doubleword sptQword04H unsigned quadword sptSbyte 05H signed byte sptSWord 06H signed wordsptSDword 07H signed doubleword sptSQword 08H signed quadword sptDeid09H 64-bit directory entry ID sptStr 0AH null-terminated string sptUni0BH unicode string sptTime 0CH Win 32 filetime sptPricing 0DH 32-bitpricing indicator sptBinary 0EH block of bytes (raw data) sptShid 0FHshabby ID (32 bits) sptLocales 10H languages/regions sptHacct 11H 32-bituser account no.The characters “spt” which are prepended to the mnemonic names in Table2 stand for “service property type.” With reference to Table 2, thesptTime type indicates that the value is in the Win32 “filetime” format,which is a well-known data format for representing time under theMicrosoft Win32 API. The sptPricing type indicates a special 32-bitpricing format which consists of an 8-bit value that indicates acurrency (such as U.S. dollars or Belgian francs), plus a 24-bit valuethat specifies an amount in the indicated currency.

With further reference to Table 2, the sptUni type indicates that thevalue is in unicode. Unicode is a standard 16-bit character set,developed by the Unicode Consortium, which includes the alphabeticcharacters of a variety of different languages. In the preferredembodiment, all string properties (including those of type sptStr) arestored by the Directory Service in Unicode, and are converted by theTreeNav methods on the client computers 102 to the appropriate charactersets for individual users.

As shown in Table 2, each property type is identified by a respective8-bit identifier. These numeric identifiers are used internally (e.g.,within the node files). to represent the corresponding property types.As with the mnemonic names for the node properties the mnemonic nameslisted in Table 2 are used by programmers for writing code.

The property types for the generic properties described above are listedin Table 3. TABLE 3 PROPERTY TYPE Name sptUni DEID sptLInt APPIDsptDword Service Group ID sptWord Icon ID sptShid Flags sptByte SecurityToken sptDword Description sptStr GoWord sptStr Search Keywords sptStrOwner sptDword Sysops sptStr Pricing sptPracing Rating sptDword Run InfosptStr Locales sptLocales Junction sptDeid Parents sptDword ChildrensptDword Access Rights sptWord Soundfile ID sptShid Banner ID sptShidDrfile ID sptShid

With further reference to FIG. 5, the property value 506 represents theactual data or information stored by the property. For example, for theproperty “Name”, the value is the null-terminated character string (inunicode) of the name of the node, and for the property DEID, theproperty value is the 64-bit DEID of the node.

5. Node Disk Structures (FIG. 6)

FIG. 6 illustrates a preferred file format which may be used byDirectory Service Providers for the storage of nodes. The specificformat shown in FIG. 6 is the format used by the Dirsrv service. As willbe apparent to those skilled in the art, various alternative fileformats and database arrangements are possible.

With reference to FIG. 6, each node file 600 contains a header portion602 which identifies the parents and children of the node, followed aproperty list portion 604 which specifies the local properties of thenode. The header portion 602 contains the number of parents of the node,followed by the DEIDs of the parents, followed by the number of childrenof the node, followed by the DEIDs of the children.

The property list portion 604 contains the number of properties in thelist, followed by a listing of the names, types and values of the node'sproperties. Specifically, for each property stored within the node file600, the property list portion 604 contains the property type(identified by the 8-bit type identifier), followed by the number ofbytes in the property name, followed by the number of bytes in theproperty value, followed by the property name 502, followed by theproperty value.

In the preferred embodiment of the Dirsrv service, node files are namedand stored according to the following convention:

-   -   filename=<DEID low part (hex)>,    -   subdirectory=<DEID high part (hex)>.        Thus, for example, the node file 600 for a node having a 64-bit        DEID of 00000000:000002A3 (hex) will have the filename 000002A3,        and will be stored in the subdirectory 00000000. If this node is        a Dirsrv node, the node file will be stored on all of the        application servers 120 of the Dirsrv service group 132. As        described below, the node files are preferably loaded from the        hard disks of the application servers 120 into main memory when        the Directory Service Providers are brought up on these servers        120.        6. Shabbies (FIG. 7)

As indicated above, the present invention provides for the separatestorage of data items that are shared by multiple nodes of the sameprovider namespace. The shared data items are stored by the DirectoryService Providers as shabbies (preferably within individual shabbyfiles), and are edited and downloaded using special methods of theTreeNav and TreeEdit APIs. A given Directory Service Provider may, butneed not, support shabbies. (As indicated above the Dirsrv servicesupports shabbies, and the BBS service does not).

In the present implementation of the network 100, four general types ofdata items are stored as shabbies: icon bitmaps, banner objects, soundfiles, and download-and-run files. As will be recognized, however,various other types of shared data items may be stored as shabbies,including, for example, video files and multimedia files.

In the preferred embodiment, every shabby has associated with it twonumeric identifiers:

SHK. (Shabby kind). This is an 8-bit number which identifies the type ofthe shabby, such as icon bitmap, banner bitmap, banner metafile, soundfile, download-and-run file, etc. Shabby kinds are assigned as new mediatypes are added.

SHN. (Shabby number). This is a 24-bit number which identifies a shabbywithin a kind, within a provider namespace.

The EnumShn method of the TreeNav API allows client applications toobtain a list of all SHNs within a given shabby kind. Thus, for example,to download all existing icons, the EnumShn method can be used by theclient to obtain a list of the SHNs of the icons, and the GetShabbymethod can then be used to retrieve the icons.

The 32-bit number <SHK,SHN> is referred to as the shabby ID, or “SHID.”Every shabby has a unique SHID within the shabby's provider namespace.To reference a shabby from a node, the SHID of the shabby is stored asan appropriate property of the node. In a present implementation, theproperties that store SHIDs are the Icon ID, Banner ID, Soundfile ID andDrfile ID properties. (Note from Table 3 above that each of these fourproperty types has a type of “sptShid.”) For example, to specify a soundfile for a node, the sysop would enter the SHID of the sound file as theSoundfile ID property of the node.

Shabbies can be divided into one of two groups, depending upon how theyare retrieved by the client:

TreeNav-able shabbies. These shabbies are retrieved via the GetShabbymethod of the TreeNav API, which returns a shabby given its SHID. Nosecurity checking is performed by the Directory Service before returningTreeNav-able shabbies.

FTM-able shabbies. These shabbies can be retrieved only via the FTM(File Transfer Manager) service. The client retrieves these shabbies byspecifying the DEID of the node, together with the name of the property(e.g., Icon ID, Banner ID, etc.) that contains the SHID of the shabby tobe downloaded. User access to the node is verified before downloadingthe shabby to the client microcomputer 102. (In the preferredembodiment, download-and-run files are the only shabbies that aredownloaded using FTM, and all others are downloaded using the TreeNavAPIs).

The most significant bit of the SHK indicates whether the shabby isTreeNav-able or FTM-able.

In the preferred embodiment of the Dirsrv service, shabby files arenamed and stored according to the following convention:

-   -   filename=<00,SHN (hex)>,    -   subdirectory=<000000,SHK (hex)>.        Thus, for example, a shabby with SHID=<SHK,SHN>=12345678 (hex)        will be stored in a file having the name 00345678, and will be        located in a subdirectory having the name 00000012. Each shabby        file simply contains the actual bytes of the shabby; no headers        or other information are contained within the shabby files.

FIG. 7 illustrates a preferred process by which a client application(such as the Explorer) obtains the bitmap for the icon of a node. Withreference to block 702, the client application (“client”) initiallyrequests the Icon ID property of the node. This may be done, forexample, using the GetChildren method or the GetProperties method of theTreeNav API. (The GetChildren and GetProperties methods are describedbelow.) With reference to block 704, the Directory Service (i.e., aparticular Directory Service Provider of the Directory Service) respondsto the request by returning the Icon ID property (i.e., the Icon IDproperty value, which is in the form of a 32-bit SHID), or, if no IconID property exists for the node, returns an error code.

With reference to blocks 708 and 710, if an error code is returned bythe Directory Service, the client displays a default icon. In thepreferred embodiment, the client selects the default icon based upon theAPPID of the node. Thus, for example, if the node is a BBS node (asindicated by the APPID), the client displays a generic BBS icon.

With reference to blocks 712-716, if an icon ID is returned by theDirectory Service, the client uses the returned Icon ID to check itsshabby cache 452 (or “icon cache” in FIG. 7) for the icon bitmap. If thebitmap if found in the shabby cache 452 (referred to as a “cache hit”),the client retrieves the bitmap from the cache 452 and displays theicon. For frequent users of the network, the cache hit rate may be veryhigh (for example, 95% or higher), since the shabby cache 452 isimplemented as a persistent (or “off-line”) cache. In the preferredembodiment, this hit rate is improved by the use of the same icon formany different nodes.

With reference to blocks 720-724, if the icon bitmap is not presentwithin the cache 452, the client generates a GetShabby call to retrievethe shabby identified by the icon ID. The Directory Service Providerresponds by reading the requested shabby (i.e., icon bitmap) from itsshabby database, and by sending the shabby over the WAN 106 to theclient. The client then displays the icon, and stores the icon bitmapwithin the shabby cache 452. As described above, because icon bitmapsare not deleted from the shabby cache 452 in the preferred embodiment,there is no need for the client to download the same bitmap twice. Inother embodiments, an LRU (least recently used) or other algorithm maybe used to delete icon bitmaps from the user's hard disk, in which casethe client may have to download the same bitmap more than once.

The FIG. 7 process of identifying, downloading and caching icon bitmapsis also applicable to other types of shabbies which may be cached by theclient. As indicated above, the types of shabbies that are cached in apresently preferred implementation of the Explorer 402 are icon bitmaps,sound files, and banner objects.

7. Server Memory Structures and Operation (FIGS. 8 and 9)

With reference to FIG. 8, each application server 120 (“Dirsrv server”)of the Dirsrv service group 132 includes a respective hard disk 802which stores all of the Dirsrv node files (representing all of the nodeswithin the Dirsrv namespace 212), and which stores all of the Dirsrvshabby files (representing all shabbies that are associated with Dirsrvnodes). To increase performance as node properties and shabbies arerequested by clients, the node files and shabby files are maintainedwithin the main memory of the Dirsrv server 120 (and all otherapplication servers of the Dirsrv service group 132). The node files arestored as C++ objects within a node table 804, and are hashed by theirrespective DEIDs. The shabby files are stored within a shabby cache 806,and are hashed by their respective SHNs (shabby numbers). As is wellknown in the art, hashing algorithms reduce the amount of time requiredto locate a data item in memory, and thereby increase performance.

In the preferred embodiment, all of the nodes (i.e., node files) areloaded into memory when the Dirsrv service is initially brought up onthe application server 120. Once a node is loaded into memory, it is notremoved from memory unless deleted via a TreeEdit operation. In otherembodiments, the nodes may be loaded and unloaded dynamically.

Shabby files are preferably loaded into memory upon request only (i.e.,a shabby is not loaded until requested via a GetShabby call). As theshabbies are loaded into memory, the Dirsrv service generates arespective hash table (not shown) for each shabby kind (i.e., for eachSHK value). Once a shabby is loaded into memory, it is not removed frommemory unless deleted via a TreeEdit operation.

Each node (stored as a C++ object) in the node table 804 consistsprimarily of a local properties cache 810 and a remote properties cache812. The local properties cache 810 contains the local properties of therespective node, and the remote properties cache 812 contains any remoteproperties that have recently been retrieved by the Dirsrv server 120.The remote property caches 812 are refreshed periodically (at afrequency that may be set via a global network registry, and with adefault of every 5 minutes), to ensure that the cached remote propertydata is relatively up-to-date. Properties stored within the local andremote properties caches 810, 812 are preferably hashed by propertyname.

With further reference to FIG. 8, the Dirsrv service maintains a Gowordindex 820 for supporting GoWord searches. The GoWord index 820 mapsGoWords to the DEIDs of the corresponding nodes, and is accessedwhenever a GetDeidFromGoWord call is received by the server 120. In thepreferred embodiment, the GoWord index 820 is generated on-the-fly asthe node files are initially loaded into memory, and is updated as nodesare added, deleted and edited via the TreeEdit methods.

With reference to FIGS. 1 and 8, whenever one of the servers 120 of thatDirsrv service group 132 receives a TreeNav call the requires an updateto a node file or a shabby file, that update transaction is forwarded tothe Arbiter service, which is a generic (i.e., non-service-specific)transaction replication service that replicates update transactionsacross groups of application servers 120. In the preferred embodiment, adedicated microcomputer (not shown) that runs the Arbiter serviceapplication is provided to handle all Dirsrv update transactions. TheArbiter service (running on the dedicated microcomputer) responds to theforwarded update transaction by broadcasting the transaction to all ofthe servers 120 of the Dirsrv service group 132 for processing. TheArbiter service also monitors the outcome of the update transaction oneach application server 120 of the Dirsrv service group 132 to ensureconsistent processing by the different servers. This process ofreplicating update transactions ensures that the node files and shabbyfiles stored by the different servers 120 of the service group 132 areidentical.

FIG. 9 illustrates the process by which the Dirsrv service (running on aparticular application server 120) responds to a request from a client(such as the Explorer) for a particular property of a particular node.The request may result from either a GetProperties call or a GetChildrencall. It may be assumed in FIG. 9 that the user's access rights to thenode have already been verified. (The GetProperties and GetChildrenmethods, and the method by which user access rights are determined, aredescribed in the following sections).

With reference to blocks 902-906, the Dirsrv server/service initiallychecks the node's local properties cache 810, and if the requestedproperty is found, returns the property value to the client. (Forcertain properties, such as the “Parents,” “Children” and “AccessRights” properties, the Dirsrv alternatively determines the propertyvalue on-the-fly.) With reference to block 910, if the requestedproperty is not found in the local properties cache 810, the Dirsrvservice compares the property name against a list of properties that arenever stored remotely, to thereby determine whether the requestedproperty may be stored remotely. In the preferred embodiment, this listconsists of the following properties: DEID, APPID, Flags, Service GroupID, GoWord, Junction, Parents, Children, Access Rights, and allproperties of type sptShid. If the requested name appears in the list(indicating that the property is not a. remote property), the Dirsrvservice returns an error code (preferably in the form of an emptyproperty) to the client to indicate that the property does not exist forthe node.

With reference to blocks 914-918, if the requested property is one whichmay be stored remotely, the Dirsrv service checks the remote propertiescache 812 for the property. If the property is found in the remoteproperties cache 812, and is not a dummy property (discussed below), theDirsrv service returns the requested property to the client. If theproperty is found but is a dummy property, the Dirsrv service returns anerror code to the client to indicate that the property does not existfor the node.

With reference to blocks 920-924, if the requested property is not foundin either the local properties cache 810 or the remote properties cache812 for the node, the Dirsrv service uses the node's APPID to determinethe remote service with which the node is associated, and then forwardsthe property request (via an RPC) to this service. If the property isreturned by the remote service, the Dirsrv service returns the propertyto the client and stores the property within the remote properties cache812 for the node.

With reference to block 926, if the remote service fails to return therequested property, the Dirsrv service returns an error code to theclient. Additionally, the Dirsrv service stores a dummy property (typesptNil, size zero) in the node's remote properties cache 812 to inhibitthe forwarding of requests for the property to the remote service.

Although FIGS. 8 and 9 (and the associated description) are directed tothe Dirsrv service, these Figures are also generally applicable to theapplication servers 120 of the BBS service group 134, with the exceptionthat the BBS service does not implement either a GoWord index 820 or ashabby cache 806. Further, the implementation depicted by these figuresis suitable for other Directory Service Providers (other than Dirsrv andBBS) that may be added to the Directory Service.

8. Junction Points (FIGS. 10A and 10B)

As described above, junction point nodes provide a seamless interfacebetween different provider namespaces, and thereby provide support formultiple namespaces. In the preferred embodiment, junction points havethe following characteristics:

1. A “junction point” bit of the Flags property is set, indicating thatthe node is a junction point.

2. The APPID property contains the APPID of the target providernamespace.

3. The “Junction” property (type sptDeid) contains the DEID of thetarget node. (All junction point nodes have this property).

4. The Name, Security Token and Locales properties are stored as remoteproperties by the target Directory Service Provider. Specifically, theName, Security Token and Locales (if specified) of the target node areused, respectively, as the Name, Security Token and Locales of thejunction point node. Thus, for example, when the Explorer requests theName of a junction point node in the Dirsrv namespace that serves as alink to a BBS folder node, the Dirsrv service passes the request to theBBS service, and the BBS service returns the Name of the target BBSfolder node.

5. Junction point nodes cannot have children.

FIG. 10A illustrates the use of a junction point node to link the Dirsrvnamespace 212 to the BBS namespace 214. In this example, the junctionpoint node is “Dirsrv 3,” and the target node is “BBS 1.” The propertiesof Dirsrv 3 are shown in the properties table 1002. In the propertiestable 802, property values that are stored remotely (by the BBS service)are shown in brackets.

As illustrated in FIG. 10A, the Name and Security Token of Dirsrv 3 areactually the Name and Security token of the target node, BBS 1, and arestored remotely by the BBS service (as local properties of BBS 1). Anoptional Locales property (not shown) may also be stored remotely. Theremaining properties of node Dirsrv 3 are stored locally by the Dirsrvservice, preferably within a node file for Dirsrv 3. As with all othertypes of nodes, Dirsrv 3 includes a DEID, Flags, an APPID, and a ServiceGroup ID. The APPID identifies the namespace of the target node. BecauseDirsrv 3 is a junction point node, it also includes a “Junction”property, which contains the DEID of the target node. Dirsrv 3 may alsoinclude an Icon ID, which contains the DEID of the Icon that will bedisplayed by the Explorer.

FIG. 10B illustrates generally how the node configuration of FIG. 10A isseen by an end user via the Explorer (assuming the user is authorized toaccess every such node). As the user navigates the nodes of the Dirsrvnamespace 212, the user sees the BBS 1 folder node as being a child ofthe Dirsrv 1 folder node, without any indication that the BBS 1 noderesides in a separate namespace on a separate application server. Whenthe user double clicks on the icon (not shown) for the BBS 1 node, theExplorer 402 launches the navigator 440 for the BBS service (using theAPPID of Dirsrv 3, which identifies the appropriate navigator), allowingthe user to view the BBS message nodes, BBS 2 and BBS 3. This process oflaunching the BBS navigator is advantageously transparent to the user.

In the presently preferred implementation, all junction points of thecontent tree 220 serve as proxies to BBS folders. Although junctionpoints could also be provided within the BBS namespace 214, the need forsuch junction points is obviated by an Explorer feature which allows theuser to move upward through the tree 220 along the same path taken toget to the current node. With reference to FIG. 10A, for example, if auser takes the path (Dirsrv 1)→(Dirsrv 3/BBS 1)→(BBS 3) to get to nodeBBS 3, the user can then move up the content tree 220 along the samepath (using either a “parent folder” option or by clicking on portionsof the map 304 within the left pane 302) to return to the level ofDirsrv 1.

9. TreeNav Methods

As described above, the TreeNav API provides the functionality needed byclient applications (such as the Explorer) to extract directoryinformation (properties, shabbies, etc.) from the various DirectoryService Providers, As will be appreciated by those of ordinary skill inthe art, the provision of the TreeNav API facilitates both the additionof new Directory Service Providers to the Directory Service and theaddition of new client applications of the Directory Service.

Table 4 lists the parameters of the primary methods of the TreeNav API.The respective functions performed by these methods are described aboveunder the heading OVERVIEW OF DIRECTORY SERVICE AND RELATED COMPONENTS.Table 5 indicates the information held by each of the parameters listedin Table 4. TABLE 4 TreeNav METHOD PARAMETERS GetProperties pdeid,nDeid, rgszProp, pLocales, pnNodes, phDyn GetChildren deid, fIncludeMe,rgszProp, pLocales, pnNodes, phDyn GetParents deid, fIncludeMe,rgszProp, pLocales, pnNodes, phDyn GetDeidFromGoWord szGoWord, pLocales,pdeid GetShabby shid, ppv, pnSize EnumShn shk, pCount, phDyn

TABLE 5 PARAMETER INFORMATION HELD BY PARAMETER pdeid Array of DEIDsnDeid Number of DEIDs in pdeid rgszProp Array of property names pLocalesList of LCIDs for locales filtering (empty list indicates that nodes offall locales should be returned) pnNodes Placeholder for number of nodesto be returned phDyn Placeholder for handle to dynamic-sized bufferwhich is used to return information to client deid A single DEID of anode fIncludeMe Flag which indicates whether the node for which the DEIDis being provided is to be included. szGoword Null-terminated GoWordshid A single Shabby ID ppv Placeholder for shabby buffer pnSizePlaceholder for size - used to return size of shabby shk A single shabbykind pCount Placeholder for 16-bit value which indicates the number(count) of shabbies for which SHNs are being returned

As described above, the methods of the TreeNav API are advantageouslystructured such that only those properties specifically requested by theclient are returned by the Directory Service. Unnecessary transfers ofproperty data over the WAN 106 are thereby avoided, and valuablebandwidth is conserved. WAN bandwidth is further conserved as a resultof the access rights filtering and locales filtering features of thepresent invention, which are described below.

10. Locales and Access Rights Filtering of Nodes (FIG. 11)

As indicated in Tables 4 and 5, the GetProperties, GetChildren,GetParents and GetDeidFromGoWord methods include a “pLocales” parameter,which allows the client to specify a locales filter to be applied on theserver side. This locales filter is preferably in the form of a list ofLCIDs (locales IDs), with each member of the list identifying a languageand/or geographic region that the client is “interested in.” In thepreferred embodiment, the locales filters are specified by end users viaa dialog box of the Explorer, through which users can select from a listof predefined locales. Users can also select an “all locales” option, inwhich case no locales-based filtering will be performed.

When a locales filter is-provided by the client in a TreeNav call, theDirectory Service excludes (i.e., does not return the requestedproperties of) any node that has a Locales property that does notinclude at least one of the locales specified in the filter. (Nodes thatdo not have a Locales property are not excluded). Thus, for example, ifthe client generates the call

-   -   GetChildren(DEID=5, locales=spanish, french)        (other parameters omitted for convenience), the Directory        Service will filter out any children of node DEID=5 that have        Locales properties which do not include either spanish or        french. When an empty list (i.e., a list with no LCID entries)        is sent by the client, the Directory Service does not perform        locales-based filtering.

Locales-based filtering provides at least two significant benefits.First, locales-based filtering allows the end user to view a customized,filtered view of the content tree 220, and allows the user to avoid theinconvenience of viewing content items that are in different languagesand/or directed to different geographic regions than the user isinterested in. Thus, for example, a user can specify that he or she isinterested only in nodes that include the Locale of “English, U.K.,” toobtain a directory of content objects that are in the English languagewhich are directed to the United Kingdom. Second, as indicated above,locales-based filtering conserves bandwidth by reducing unnecessary datatransfers over the WAN 106. This, in-turn, increases performance fromthe viewpoint of the user.

Although nodes are filtered in the preferred embodiment based onuser-specified language and geographic region filters, it will bereadily apparent that other types of filters can be employed. Forexample, in other embodiments users may be able to specify a “mediatype” filter in order to select nodes of a particular media type (suchas text, still picture, video, sound, multimedia or animation). Ageneric “media type” property may then be defined to allow sysops tospecify the media type or types of the nodes they create.

FIG. 11 illustrates the sequence of steps that are performed by aDirectory Service Provider (on a particular Directory Serviceapplication server 120) to determine whether a particular node should beshown to a particular user. This determination is made for each nodethat is the subject of a GetProperties, GetChildren, GetParents orGetDeidFromGoWord call. Thus, for example, if a GetChildren(Node5) callis received by the Directory Service, and node 5 has ten children, thesequence of steps of FIG. 11 will be performed 10 times—once for eachchild node.

With reference to block 1102, the Directory Service Provider initiallyreads the node's 32-bit security token, which is stored as the SecurityToken property of the node. As described above, the security tokenidentifies a single content category to which the node has been assigned(typically by system administrators) for security purposes. In thepreferred embodiment of the network 100, various predefined contentcategories exist such as “internal public content,” “Internet publiccontent,” “18-and-older content,” “corporation X beta test data,” etc.,and different users are assigned different access rights (via the accessrights database 152) with respect to different content categories. Everynode of the content tree 220 has a security token, and is assigned toexactly one content category.

With reference to block 1104, the Directory Service Provider generates aGetAccountRights call to determine whether or not the user has accessrights with respect to the content category of the node. The parametersof the GetAccountRights API are the user's 32-bit user ID and the 32-bitsecurity token. The GetAccountRights API includes code which generatesuser-specific queries of the access rights database 152, and includescode which implements an access rights cache (not shown) within eachapplication server 120 that generates GetAccountRights calls. Apreferred implementation of the access rights database 152 and theaccess rights cache are described in a concurrently filed, commonlyassigned U.S. application having the title SYSTEM AND METHOD FORCONTROLLING ACCESS TO DATA ENTITIES IN A COMPUTER NETWORK, which isincorporated herein by reference.

The GetAccountRights API returns either (1) a code which indicates thatthe user is not authorized to access the content category (and that theuser is thus not authorized to access the node), or (2) a 16-bit accessrights value which specifies the access rights (in the form of privilegelevels) of the user with respect to the content category. With referenceto blocks 1106 and 1108, if the GetAccountRights API returns a codeindicating that the user is not authorized to access the node (orequivalently, that the user has no access rights with respect to thenode), no properties of the node are returned to the client, and theicon and properties of the node are not made visible to the user. (Fromthe viewpoint of the user and the client application, the unaccessiblenode does not exist.)

With reference to blocks 1112 and 1114, if an access rights value isreturned by the GetAccountRights API, indicating that the user has atleast some access rights with respect to the node (and specifically, atleast viewer-level access rights), the Directory Service Provider checksthe Locales parameter of the TreeNav call to see if a locales filter hasbeen provided by the client. If no locales filter was provided,indicating that no locales filtering should be performed, the DirectoryService Provider returns the property or properties requested by theclient. (As indicated above, if a requested property does not exist, theDirectory Service Provider returns an empty property to the client.) Asindicated by blocks 1114 and 1118, if a locales filter has been providedbut the node does not have a locales property, the Directory ServiceProvider similarly returns the requested property or properties.

With reference to block 1120, if a locales filter has been provided andthe node has a locales property, the list of LCIDs in the filter iscompared against the LCIDs of the node. With reference to block 1122, ifat least one of the LCIDs in the filter appears in the node's LCID list,the Directory Service Provider returns the requested property orproperties of the node to the client. Otherwise, the Directory ServiceProvider does not return any of the node's properties.

As will be readily apparent to those skilled in the art, a number ofbenefits are achieved by returning node properties only when the user isauthorized to access the node. For example, the user sees only thoseservice areas (nodes) to which he or she has access, and is notinconvenienced with having to see icons that cannot be opened. Further,a high level of security is provided against hackers, since users cannotsee or otherwise obtain information about nodes to which they have noaccess rights. Further, as indicated above, WAN bandwidth is conserved,since properties are not unnecessarily passed to the client.

11. Other Embodiments

Although the various aspects and features of the present invention havebeen described in terms of a preferred implementation of an on-lineservices network 100, this network implementation has been presented byway of example only, and is not intended to limit the scope of theinvention. Accordingly, the scope of the present invention is intendedto be defined only by reference to the following claims and theirequivalents.

1-28. (Canceled)
 29. A distributed directory service for providing usersof a computer network with a hierarchical directory of content entitieson said network, comprising: a plurality of different serviceapplications running on a plurality of different groups of applicationservers to implement a plurality of different services, each of saidservices storing a respective plurality of content nodes within arespective hierarchical directory structure; and a plurality of junctionnodes stored on said plurality of application servers, said junctionnodes linking content nodes of different hierarchical directorystructures to thereby form an integrated hierarchical directorystructure.
 30. A directory service according to claim 29, wherein saidintegrated hierarchical directory structure is a directed acyclic graph.31. A directory service according to claim 29, wherein each of saidjunction nodes serves as a proxy within one hierarchical directorystructure for a corresponding content node of a different hierarchicaldirectory structure.
 32. A directory service according to claim 29,wherein each of said junction nodes provides user-transparent linkbetween two of said hierarchical directory structures.
 33. A directoryservice according to claim 29, further comprising an application programinterface (API) for allowing client applications to navigate and accesssaid content nodes stored by said plurality of different services usinga common set of API methods, said API implemented at least in-part byeach of said plurality of different service applications.
 34. Adirectory service according to claim 29, wherein said content nodesstored by said plurality of different services represent on-lineservices and associated data entities of an on-line services network.35. A directory service according to claim 29, further comprising aclient application configured to allow a user to interactively navigatesaid integrated hierarchical directory structure via a graphical userinterface.
 36. A directory service according to claim 35, wherein saidclient application comprises a plurality of navigation modulescorresponding, respectively, to said plurality of different services.37-53. (Canceled)
 54. A node of a hierarchical directory structure, saidnode stored on an application server of an on-line services network,said node representing a service entity which may be accessed by usersof said network via client applications running on client computers,said node comprising: a first property stored within a memory of saidapplication server, said first property comprising a textual descriptionof said content entity; and a second property stored within said memoryof said application server, said second property identifying a serviceapplication corresponding to said service entity, said serviceapplication providing user access to said service entity.
 55. A nodeaccording to claim 54, further comprising a remote properties cache onsaid application server, said remote properties cache temporarilystoring at least one remote property of said node, said at least oneremote property generated remotely by said service application.
 56. Anode according to claim 54, further comprising a third property storedwithin said memory of said application server, said third propertyspecifying a security category of said node.
 57. A node according toclaim 54, further comprising a third property stored within said memoryof said application server, said third property specifying at least onelanguage of said node.
 58. A node according to claim 54, furthercomprising a third property stored within said memory of saidapplication server, said third property specifying at least onegeographic region to which said node applies.
 59. A node according toclaim 54, further comprising a third property stored within said memoryof said application server, said third property specifying adownloadable icon bitmap which corresponds to said node.
 60. A nodeaccording to claim 54, further comprising a third property stored withinsaid memory of said application server, said third property specifying adownloadable sound file which corresponds to said node, said sound filespecifying sounds generated on said client computers in association withsaid node.
 61. A node according to claim 54, further comprising a thirdproperty stored within said memory of said application server, saidthird property specifying a download-and-run file which corresponds tosaid node.
 62. A node according to claim 54, further comprising a thirdproperty stored within said memory of said application server, saidthird property specifying a downloadable banner object which correspondsto said node.
 63. A node according to claim 54, further comprising athird property stored within said memory of said application server,said third property specifying at least one parent node of said node.64. A node according to claim 54, further comprising a third propertystored within said memory of said application server, said thirdproperty specifying a content rating of said service entity.
 65. A nodeaccording to claim 54, further comprising a third property stored withinsaid memory of said application server, said third property specifying aprice associated with accessing said service entity. 66-69. (Canceled)70. A distributed directory service according to claim 29, furthercomprising a client application that runs on a computer of a user andcommunicates over the network with the plurality of different serviceapplications using a common application program interface, the clientapplication configured to request node properties from the plurality ofdifferent service applications in response to actions of the user, andto use node properties returned by the plurality of different serviceapplications to generate and display a graphical representation of theintegrated, hierarchical directory structure.
 71. (Canceled)